The crosses are made from palm fronds by members of our congregation as an annual event in time for Holy Week. We usually ( invariably ? ) use fronds of Phoenix palms, which are fairly common but officially regarded as weeds. ( Or not, depending on just where you are and what the local council thinks. There are plenty of them around anyway. )
The palm crosses are blessed during the service in which they are distributed, then either distributed to the congregation immediately, or placed where people can collect them for themselves - for example, somewhere near the communion rail, or by the church door.
We used the crosses in two of our services :